Stable AC Voltages For Testing?

[maxkracht]

I have a little $20-30 panel meter sitting on my bench that reads voltage and current coming out of my variac. I regret not setting that up sooner. Cheap modern variacs are fine, but you get what you pay for. Going the vintage route was probably a better move.

[syscokid]

I hope so. Having a cool test tool like a Variac was something that has been in the back of my mind for years.

[wpaulvogel]

Having a variac is a great thing. I’m going to suggest that you stop worrying so much about input voltage stability while checking voltages though. This is a situation that is pretty much out of your control and I find that while we want precise voltage stability, it’s nearly impossible. I have a dedicated voltmeter on my bench for displaying line voltage and it gives me something to glance at when I work. I’m not going to spend $5000 for a real power supply so it’s what it is. Setting bias and such isn’t an exact science. And although voltage variations are going to change the dissipation once you’ve found the sweet spot for the amp, you’re finished. I repair amps and what’s happening in my shop is what I have. Once the amp goes to whoever owns it, of course is a different situation. OCD is great with amps but you have to accept variables outside of your control. 70% dissipation is not a hard deck limit. It’s just a place we need to be aware of when we’re there. Most cathode biased amps idle way over 70%.

[sluckey]

The line voltage at my house varies from about 115 to 125 over the course of a typical day. I use a variac with an add-on volt/current meter to set the voltage to 120V whenever recording voltage readings . A typical amp usually takes less than 10 minutes to check and record every voltage in the amp. Even though my house voltage changes considerably over a 24 hour period, it does remain fairly constant over a 30 minute period, more than sufficient for what I need when recording voltages.

You can see my modified variac on pages 5 and 6 of this pdf. This mod can be adapted to almost any variac.

https://sluckeyamps.com/misc/Amp_Scrapbook.pdf

[mike-p]

I have an always on UPS, an eaton 9130, for computers and data centers etc, any reason not to use one of these for voltage regulation and dealing with dirty AC?

[WhopperPlate]

I have an always on UPS, an eaton 9130, for computers and data centers etc, any reason not to use one of these for voltage regulation and dealing with dirty AC?

I have always wondered about these . Manual says Voltage regulation is +-3%.

[syscokid]

You can see my modified variac on pages 5 and 6 of this pdf. This mod can be adapted to almost any variac.

https://sluckeyamps.com/misc/Amp_Scrapbook.pdf

Nice! Thanks for posting this.

[ViperDoc]

Look into rack mountable Furman power regulators, not a conditioner. The lowest Furman option on Sweetwater goes for $900, then $1600 and up. Whereas a conditioner will handle transient power spike noise, it won't regulate the voltage in real time like a regulator will (to the best it can), and that's why it's more money for more honey. Or you can ride the variac analog style.

[WhopperPlate]

Look into rack mountable Furman power regulators, not a conditioner. The lowest Furman option on Sweetwater goes for $900, then $1600 and up. Whereas a conditioner will handle transient power spike noise, it won't regulate the voltage in real time like a regulator will (to the best it can), and that's why it's more money for more honey. Or you can ride the variac analog style.

I have used these heavily for years doing live sound . Hundreds of gigs. Reliable in my experience.

https://www.bhphotovideo.com/c/product/ ... pdEALw_wcB

[ViperDoc]

Looks really good for the money.